216 BOARD OF AGRICULTURE. 



Tbere was 



Nitrogen in the albuminoids 113 



Phosphoric acid in the ash. , 44 



Potash 120 



Soda 17 



Lime 60 



Silica, iron, etc 150 



Magnesia 17 



*t)' 



Total .. 521 lbs. 



Commencing at the bottom of the list we may strike out the seven- 

 teen pounds of magnesia, for soils, as a rule, contain all of this 

 substance that is needed ; there are exceptional cases where the 

 application of magnesia is beneficial. The one hundred and fifty 

 pounds of silica may be set aside at once ; plants get this substance 

 in abundance, for as a matter of fact it is not essential to the growth, 

 but seems an accidental constituent of no special use. 



Of the sixty pounds of lime it may be said, that on most soils it 

 is unnecessary to apply it, but even if a soil is deficient in lime, we 

 shall more than make good this deficiency in almost any form of fer- 

 tilizer we may use, for manures and fertilizers all contain a good 

 percentage of lime. 



The seventeen pounds of soda is of no use to the plant, and even 

 if essential it is abundantly supplied bj' the soil. 



But here our work of setting aside must end. Potash is one of 

 the substances that becomes exhausted in soils that have been 

 cropped for a considerable time. 



Phosphoric acid is another, substance that must be used to restore 

 fertility to worn soils. 



Nitrogen is an element about which little is known. It is pretty 

 well understood that plants have the power of getting a consider- 

 able portion of their nitrogen from the soil without application from 

 external sources, but this power seems to depend upon the kind of 

 plant to a considerable degree. It is also known that application of 

 manures containing nitrogen are beneficial, but just how much of the 

 nitrogen a crop can supply itself with, and how much may profitably 

 be applied to the soil, is an open question and likely to remain so 

 for some time. 



We may now define the term 



PLANT FOOD. 



It is any substance that can contribute towards the growth of a plant. 



